The present invention relates to aircraft and, more particularly, to rotor-wing aircraft having an adjustable tail nozzle.
The rotor/wings or blades of conventional rotary wing or rotor-wing aircraft are frequently driven by a rotating shaft or mast that rotates about a generally vertical axis. The rotating blades and shaft cause a reaction torque that is frequently counter-balanced by smaller rotor blades mounted on the aircraft tail so they rotate about a generally horizontal axis. In other cases, the reaction torques are counter-balanced by having two counter-rotating main rotor blade sets. In order to avoid the problems associated with reaction torques, some rotary wing aircraft are reaction driven. That is, the rotor/wings are rotated by high-pressure gas exhausted from a trailing edge of each wing. Because reaction-driven aircraft are not shaft driven, significant reaction torques are not transmitted to the aircraft body. The gas delivered to each wing of a reaction-driven aircraft is typically created by a power plant (e.g., a gas turbine engine) mounted in the aircraft body and directed to the rotor/wing through the rotor mast.
Higher performance rotor-wing aircraft are sought. If reaction-drive rotor-wing aircraft are used, increasing performance generally requires increased exhaust mass flow rates and operating pressures. However, reaction-drive rotor-wing aircraft have significant system losses. Reaction-drive rotor-wing aircraft also require a relatively thick rotor mast and relatively large rotor blades to accommodate the exhaust passing through them during aircraft operation. In addition, heavy metal parts are required for transferring the high-temperature exhaust from the power plant to the blade tips. Further, the larger mast and blades increase aircraft weight and drag, requiring even larger power plants, which increase fuel usage and cost.
In addition, there is a need for increased vertical thrust during vertical flight of rotor-wing aircraft. One method for providing more thrust is to provide a second rotor/wing. Another method for providing more thrust is to provide a vertical fan in the aircraft. However, adding a second rotor/wing or adding a vertical fan greatly increases the complexity of the required drive train, manufacturing cost, and the weight of the aircraft. A rotor-wing aircraft design is sought that is more efficient than conventional reaction-drive rotor-wing aircraft and provides increased vertical thrust.